Re: [PATCH v2] kernel: Expose SYS_kcmp by default
On 05/02/2021 22.06, Chris Wilson wrote:
> Userspace has discovered the functionality offered by SYS_kcmp and has
> started to depend upon it. In particular, Mesa uses SYS_kcmp for
> os_same_file_description() in order to identify when two fd (e.g. device
> or dmabuf) point to the same struct file. Since they depend on it for
> core functionality, lift SYS_kcmp out of the non-default
> CONFIG_CHECKPOINT_RESTORE into the selectable syscall category.
>
> Note that some distributions such as Ubuntu are already enabling
> CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp.
>
Looks a lot like
https://lore.kernel.org/lkml/20200710075632.14661-1-li...@rasmusvillemoes.dk/.
So FWIW, ack from me.
cc += Cyrill.
> References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046
> Signed-off-by: Chris Wilson
> Cc: Kees Cook
> Cc: Andy Lutomirski
> Cc: Will Drewry
> Cc: Andrew Morton
> Cc: Dave Airlie
> Cc: Daniel Vetter
> Cc: Lucas Stach
> Acked-by: Daniel Vetter # DRM depends on SYS_kcmp
>
> ---
> v2:
> - Default n.
> - Borrrow help message from man kcmp.
> - Export get_epoll_tfile_raw_ptr() for CONFIG_KCMP
> ---
> fs/eventpoll.c| 4 ++--
> include/linux/eventpoll.h | 2 +-
> init/Kconfig | 12
> kernel/Makefile | 2 +-
> tools/testing/selftests/seccomp/seccomp_bpf.c | 2 +-
> 5 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index a829af074eb5..3196474cbe24 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -979,7 +979,7 @@ static struct epitem *ep_find(struct eventpoll *ep,
> struct file *file, int fd)
> return epir;
> }
>
> -#ifdef CONFIG_CHECKPOINT_RESTORE
> +#ifdef CONFIG_KCMP
> static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned
> long toff)
> {
> struct rb_node *rbp;
> @@ -1021,7 +1021,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file,
> int tfd,
>
> return file_raw;
> }
> -#endif /* CONFIG_CHECKPOINT_RESTORE */
> +#endif /* CONFIG_KCMP */
>
> /**
> * Adds a new entry to the tail of the list in a lockless way, i.e.
> diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
> index 0350393465d4..593322c946e6 100644
> --- a/include/linux/eventpoll.h
> +++ b/include/linux/eventpoll.h
> @@ -18,7 +18,7 @@ struct file;
>
> #ifdef CONFIG_EPOLL
>
> -#ifdef CONFIG_CHECKPOINT_RESTORE
> +#ifdef CONFIG_KCMP
> struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned
> long toff);
> #endif
>
> diff --git a/init/Kconfig b/init/Kconfig
> index b77c60f8b963..1b75141bc18b 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1194,6 +1194,7 @@ endif # NAMESPACES
> config CHECKPOINT_RESTORE
> bool "Checkpoint/restore support"
> select PROC_CHILDREN
> + select KCMP
> default n
> help
> Enables additional kernel features in a sake of checkpoint/restore.
> @@ -1737,6 +1738,17 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS
> config ARCH_HAS_MEMBARRIER_SYNC_CORE
> bool
>
> +config KCMP
> + bool "Enable kcmp() system call" if EXPERT
> + default n
> + help
> + Enable the kernel resource comparison system call. It provides
> + user-space with the ability to compare two processes to see if they
> + share a common resource, such as a file descriptor or even virtual
> + memory space.
> +
> + If unsure, say N.
> +
> config RSEQ
> bool "Enable rseq() system call" if EXPERT
> default y
> diff --git a/kernel/Makefile b/kernel/Makefile
> index aa7368c7eabf..320f1f3941b7 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -51,7 +51,7 @@ obj-y += livepatch/
> obj-y += dma/
> obj-y += entry/
>
> -obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
> +obj-$(CONFIG_KCMP) += kcmp.o
> obj-$(CONFIG_FREEZER) += freezer.o
> obj-$(CONFIG_PROFILING) += profile.o
> obj-$(CONFIG_STACKTRACE) += stacktrace.o
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c
> b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 26c72f2b61b1..1b6c7d33c4ff 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -315,7 +315,7 @@ TEST(kcmp)
> ret = __filecmp(getpid(), getpid(), 1, 1);
> EXPECT_EQ(ret, 0);
> if (ret != 0 && errno == ENOSYS)
> - SKIP(return, "Kernel does not support kcmp() (missing
> CONFIG_CHECKPOINT_RESTORE?)");
> + SKIP(return, "Kernel does not support kcmp() (missing
> CONFIG_KCMP?)");
> }
>
> TEST(mode_strict_support)
>
Re: [PATCH v2] kernel: Expose SYS_kcmp by default
On Fri, Feb 5, 2021 at 10:28 PM Chris Wilson wrote: > > Quoting Kees Cook (2021-02-05 21:20:33) > > On Fri, Feb 05, 2021 at 09:16:01PM +, Chris Wilson wrote: > > > The subject should of course be changed, as it is no longer being > > > enabled by default. > > > > "default n" is redundant. > > I thought being explicit would be preferred. There are a few other > default n, so at least it's not the odd-one-out! > > > I thought Daniel said CONFIG_DRM needed to > > "select" it too, though? > > Yes. We will need to select it for any DRM driver so that the Vulkan/GL > stacks can rely on having SYS_kcmp. That deserves to be handled and > explain within drm/Kconfig, and as they are already shipping with calls > to SYS_kcmp we may have to ask for a stable backport. Oh I dreamed and thought it's part of this patch already. So v3 with matching subject to enabled it for drm? -Daniel > > > Otherwise, yeah, this looks good. Was the > > export due to the 0-day bot failure reports? > > Yes. > -Chris -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
Re: [PATCH v2] kernel: Expose SYS_kcmp by default
Quoting Kees Cook (2021-02-05 21:20:33) > On Fri, Feb 05, 2021 at 09:16:01PM +, Chris Wilson wrote: > > The subject should of course be changed, as it is no longer being > > enabled by default. > > "default n" is redundant. I thought being explicit would be preferred. There are a few other default n, so at least it's not the odd-one-out! > I thought Daniel said CONFIG_DRM needed to > "select" it too, though? Yes. We will need to select it for any DRM driver so that the Vulkan/GL stacks can rely on having SYS_kcmp. That deserves to be handled and explain within drm/Kconfig, and as they are already shipping with calls to SYS_kcmp we may have to ask for a stable backport. > Otherwise, yeah, this looks good. Was the > export due to the 0-day bot failure reports? Yes. -Chris
Re: [PATCH v2] kernel: Expose SYS_kcmp by default
On Fri, Feb 05, 2021 at 09:16:01PM +, Chris Wilson wrote:
> The subject should of course be changed, as it is no longer being
> enabled by default.
"default n" is redundant. I thought Daniel said CONFIG_DRM needed to
"select" it too, though? Otherwise, yeah, this looks good. Was the
export due to the 0-day bot failure reports?
-Kees
>
> Something like
>
> kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
>
> Quoting Chris Wilson (2021-02-05 21:06:10)
> > Userspace has discovered the functionality offered by SYS_kcmp and has
> > started to depend upon it. In particular, Mesa uses SYS_kcmp for
> > os_same_file_description() in order to identify when two fd (e.g. device
> > or dmabuf) point to the same struct file. Since they depend on it for
> > core functionality, lift SYS_kcmp out of the non-default
> > CONFIG_CHECKPOINT_RESTORE into the selectable syscall category.
> >
> > Note that some distributions such as Ubuntu are already enabling
> > CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp.
> >
> > References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046
> > Signed-off-by: Chris Wilson
> > Cc: Kees Cook
> > Cc: Andy Lutomirski
> > Cc: Will Drewry
> > Cc: Andrew Morton
> > Cc: Dave Airlie
> > Cc: Daniel Vetter
> > Cc: Lucas Stach
> > Acked-by: Daniel Vetter # DRM depends on SYS_kcmp
> >
> > ---
> > v2:
> > - Default n.
> > - Borrrow help message from man kcmp.
> > - Export get_epoll_tfile_raw_ptr() for CONFIG_KCMP
> > ---
> > fs/eventpoll.c| 4 ++--
> > include/linux/eventpoll.h | 2 +-
> > init/Kconfig | 12
> > kernel/Makefile | 2 +-
> > tools/testing/selftests/seccomp/seccomp_bpf.c | 2 +-
> > 5 files changed, 17 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> > index a829af074eb5..3196474cbe24 100644
> > --- a/fs/eventpoll.c
> > +++ b/fs/eventpoll.c
> > @@ -979,7 +979,7 @@ static struct epitem *ep_find(struct eventpoll *ep,
> > struct file *file, int fd)
> > return epir;
> > }
> >
> > -#ifdef CONFIG_CHECKPOINT_RESTORE
> > +#ifdef CONFIG_KCMP
> > static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned
> > long toff)
> > {
> > struct rb_node *rbp;
> > @@ -1021,7 +1021,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file
> > *file, int tfd,
> >
> > return file_raw;
> > }
> > -#endif /* CONFIG_CHECKPOINT_RESTORE */
> > +#endif /* CONFIG_KCMP */
> >
> > /**
> > * Adds a new entry to the tail of the list in a lockless way, i.e.
> > diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
> > index 0350393465d4..593322c946e6 100644
> > --- a/include/linux/eventpoll.h
> > +++ b/include/linux/eventpoll.h
> > @@ -18,7 +18,7 @@ struct file;
> >
> > #ifdef CONFIG_EPOLL
> >
> > -#ifdef CONFIG_CHECKPOINT_RESTORE
> > +#ifdef CONFIG_KCMP
> > struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned
> > long toff);
> > #endif
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index b77c60f8b963..1b75141bc18b 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1194,6 +1194,7 @@ endif # NAMESPACES
> > config CHECKPOINT_RESTORE
> > bool "Checkpoint/restore support"
> > select PROC_CHILDREN
> > + select KCMP
> > default n
> > help
> > Enables additional kernel features in a sake of
> > checkpoint/restore.
> > @@ -1737,6 +1738,17 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS
> > config ARCH_HAS_MEMBARRIER_SYNC_CORE
> > bool
> >
> > +config KCMP
> > + bool "Enable kcmp() system call" if EXPERT
> > + default n
> > + help
> > + Enable the kernel resource comparison system call. It provides
> > + user-space with the ability to compare two processes to see if
> > they
> > + share a common resource, such as a file descriptor or even virtual
> > + memory space.
> > +
> > + If unsure, say N.
> > +
> > config RSEQ
> > bool "Enable rseq() system call" if EXPERT
> > default y
> > diff --git a/kernel/Makefile b/kernel/Makefile
> > index aa7368c7eabf..320f1f3941b7 100644
> > --- a/kernel/Makefile
> > +++ b/kernel/Makefile
> > @@ -51,7 +51,7 @@ obj-y += livepatch/
> > obj-y += dma/
> > obj-y += entry/
> >
> > -obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
> > +obj-$(CONFIG_KCMP) += kcmp.o
> > obj-$(CONFIG_FREEZER) += freezer.o
> > obj-$(CONFIG_PROFILING) += profile.o
> > obj-$(CONFIG_STACKTRACE) += stacktrace.o
> > diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c
> > b/tools/testing/selftests/seccomp/seccomp_bpf.c
> > index 26c72f2b61b1..1b6c7d33c4ff 100644
> > --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> > +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> > @@ -315,7 +315,7 @@ TEST(kcmp)
> > ret = __filecmp(getpid(), getpid(), 1, 1);
Re: [PATCH v2] kernel: Expose SYS_kcmp by default
The subject should of course be changed, as it is no longer being
enabled by default.
Something like
kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
Quoting Chris Wilson (2021-02-05 21:06:10)
> Userspace has discovered the functionality offered by SYS_kcmp and has
> started to depend upon it. In particular, Mesa uses SYS_kcmp for
> os_same_file_description() in order to identify when two fd (e.g. device
> or dmabuf) point to the same struct file. Since they depend on it for
> core functionality, lift SYS_kcmp out of the non-default
> CONFIG_CHECKPOINT_RESTORE into the selectable syscall category.
>
> Note that some distributions such as Ubuntu are already enabling
> CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp.
>
> References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046
> Signed-off-by: Chris Wilson
> Cc: Kees Cook
> Cc: Andy Lutomirski
> Cc: Will Drewry
> Cc: Andrew Morton
> Cc: Dave Airlie
> Cc: Daniel Vetter
> Cc: Lucas Stach
> Acked-by: Daniel Vetter # DRM depends on SYS_kcmp
>
> ---
> v2:
> - Default n.
> - Borrrow help message from man kcmp.
> - Export get_epoll_tfile_raw_ptr() for CONFIG_KCMP
> ---
> fs/eventpoll.c| 4 ++--
> include/linux/eventpoll.h | 2 +-
> init/Kconfig | 12
> kernel/Makefile | 2 +-
> tools/testing/selftests/seccomp/seccomp_bpf.c | 2 +-
> 5 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index a829af074eb5..3196474cbe24 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -979,7 +979,7 @@ static struct epitem *ep_find(struct eventpoll *ep,
> struct file *file, int fd)
> return epir;
> }
>
> -#ifdef CONFIG_CHECKPOINT_RESTORE
> +#ifdef CONFIG_KCMP
> static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned
> long toff)
> {
> struct rb_node *rbp;
> @@ -1021,7 +1021,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file,
> int tfd,
>
> return file_raw;
> }
> -#endif /* CONFIG_CHECKPOINT_RESTORE */
> +#endif /* CONFIG_KCMP */
>
> /**
> * Adds a new entry to the tail of the list in a lockless way, i.e.
> diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
> index 0350393465d4..593322c946e6 100644
> --- a/include/linux/eventpoll.h
> +++ b/include/linux/eventpoll.h
> @@ -18,7 +18,7 @@ struct file;
>
> #ifdef CONFIG_EPOLL
>
> -#ifdef CONFIG_CHECKPOINT_RESTORE
> +#ifdef CONFIG_KCMP
> struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned
> long toff);
> #endif
>
> diff --git a/init/Kconfig b/init/Kconfig
> index b77c60f8b963..1b75141bc18b 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1194,6 +1194,7 @@ endif # NAMESPACES
> config CHECKPOINT_RESTORE
> bool "Checkpoint/restore support"
> select PROC_CHILDREN
> + select KCMP
> default n
> help
> Enables additional kernel features in a sake of checkpoint/restore.
> @@ -1737,6 +1738,17 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS
> config ARCH_HAS_MEMBARRIER_SYNC_CORE
> bool
>
> +config KCMP
> + bool "Enable kcmp() system call" if EXPERT
> + default n
> + help
> + Enable the kernel resource comparison system call. It provides
> + user-space with the ability to compare two processes to see if they
> + share a common resource, such as a file descriptor or even virtual
> + memory space.
> +
> + If unsure, say N.
> +
> config RSEQ
> bool "Enable rseq() system call" if EXPERT
> default y
> diff --git a/kernel/Makefile b/kernel/Makefile
> index aa7368c7eabf..320f1f3941b7 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -51,7 +51,7 @@ obj-y += livepatch/
> obj-y += dma/
> obj-y += entry/
>
> -obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
> +obj-$(CONFIG_KCMP) += kcmp.o
> obj-$(CONFIG_FREEZER) += freezer.o
> obj-$(CONFIG_PROFILING) += profile.o
> obj-$(CONFIG_STACKTRACE) += stacktrace.o
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c
> b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 26c72f2b61b1..1b6c7d33c4ff 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -315,7 +315,7 @@ TEST(kcmp)
> ret = __filecmp(getpid(), getpid(), 1, 1);
> EXPECT_EQ(ret, 0);
> if (ret != 0 && errno == ENOSYS)
> - SKIP(return, "Kernel does not support kcmp() (missing
> CONFIG_CHECKPOINT_RESTORE?)");
> + SKIP(return, "Kernel does not support kcmp() (missing
> CONFIG_KCMP?)");
> }
>
> TEST(mode_strict_support)
> --
> 2.20.1
>
